Preheat the oven to 180C/350F. Grease a large baking dish and set it aside.
In a deep pot or saucepan, melt your butter. Once it is melted, add your chopped chayote and water. Cover the pan and let it simmer for 7-8 minutes, or until tender. Once the squash is tender, add the rest of the ingredients and mix well, until combined. Continue to simmer for a further 3 minutes.
Remove the mock apple filling from the heat and transfer it into the lined baking dish. Bake in the oven for 8-10 minutes. While the filling is baking, prepare your crisp topping.
In a mixing bowl, add all your crisp topping ingredients and mix well. Remove the baking dish from the oven and sprinkle the crisp all over the top. Place back in the oven and bake for 10-15 minutes, or until the tops are golden brown.
Remove from the oven and let sit for 10 minutes, before serving.
* This makes around 1kg/2 lbs chopped squash. You can also use yellow squash or zucchini. ** I used sugar free brown sugar, but erythritol and monk fruit sweetener can also be used. TO STORE: The apple crumble can be stored in the refrigerator, covered. It will keep well for up to 1 week.TO FREEZE: Place leftover crisp in a shallow container and store in the freezer for up to 6 monthsTO REHEAT: Apple crisp should never be microwaved. Place the crisp in a preheated oven and heat up until warm.